Mechanical Properties of Concrete Mechanical Properties of Concrete Reinforced with ARReinforced with AR--Glass FibersGlass FibersT. Desai*, R. Shah*, A. Peled+, and B. Mobasher** Dept of Civil and Env. Eng., Arizona State Univ., Tempe, AZ, USA+ Structural Eng. Dept., Ben Gurion University, Beer Sheva, Israel7thInternational Conference on Brittle-Matrix Composites, BMC-7Warsaw, Poland, October 13-15th, 2003Scope of PresentationScope of Presentationu Reinforcing Mechanismsu Filament Winding Processing u Experimental Programu Theoretical aspect of Composite Laminatesu Results and Discussionsu ConclusionsAR Glass Fiber TypesAR Glass Fiber Typesu Two types of AR Glass fibers, HP and HD were used.u Source: VETROTEX, Cem-FIL, SAINT-GOBAIN u chopped strand form.u High dispersion (HD) AR-Glass fibers u disperse thoroughly throughout the mixtures. u controlling and prevention of early shrinkage plastic cracking. u High performance (HP) AR-Glass fibers u maintain the bundle characteristics throughout the mixing and casting, u increase concrete's flexural strength, ductility, toughness.2.51.5-3.570150-380126,12,24Glass(AR)Densityg/cm3UltimateElongation%ElasticModulusGPaTensileStrengthMPaDiameterMicronLengthmmFiberToughening Due to Fiber BridgingToughening Due to Fiber Bridgingu Fiber Debonding and pulloutu Closing Pressureu Crack face stiffnessu Stress Intensity reductionu Crack closurec0afIaK=P*(U)g(1,)daξξ∫0faaIFfIPaaK2COD= P* (U) Kd d E'F∂ξη∂∫∫R+ nRm ∆1 R+ Rm ∆n2 R+ Rm ∆n2 Rm R+ Rm ∆n2 Rm RR+ nRm ∆1 R+ Rm ∆n2 ∆aIntroduction to RIntroduction to R--CurvesCurvesPotential Energy Approach:u(x) = crack opening profileGreen’s function Approach:G(a,x) = green’s functiona = crack lengthlb= bridging zone lengthσb= bridging stress02blbbduR(u)dxdx∆=σ∫0blbbbK(l)G(a,x)(x)dx∆=σ∫Formulation of Theoretical RFormulation of Theoretical R--CurvesCurvesu Notch Sensitivityu Failure Conditions, Stable and unstable crack growth11 LEFM Quasi Brittle Materialsα=α>0, >∂∂>∂∂=aGaRGRaGaRGR∂∂=∂∂== ,γCritical Condition0a+ a = b∆αG, Rac =a0+∆a = αa∆aa0∆a(1) stable(2) criticalMix FormulationMix Formulation0.550.4Water/Cement Ratio751578Fine Aggregates38830010-5 mm Aggregates60046020-10 mm Aggregates341876Cementitious materials(Cement + flyash,fa/C=0.1)Type #2, KgType #1, KgDry weight per m3Mixtures MatrixMixtures MatrixMIX ID Fiber Length Vf Compression Test Flexure Test mm Kg/m3 Age of Curing Age of Curing 3 days 7 days 28 days 28 days Control NA NA - - - 3 HP6_10 6 10 - - - 3 HP12_10 12 10 2* 2 2 3 HP24_10 24 10 - - - 3 HP612_10 6,12 10 - - - 3 HP624_10 6,24 10 - - - 3 HP1224_10 12,24 10 2 2 2 3 HP61224_10 6,12,24 10 - - - 3 HP1224_20 12,24 20 - - - 3 HP12_20 12 20 2 2 2 3 HD12_20 12 20 - - - 3Scope of WorkScope of Worku Comparison of fiber dispersion characteristics. u Dosage of high dispersion (HD) fibers = 0.6, 5, and 20 Kg/m3. u Dosage of high performance (HP) fibers = 5, 10, and 20 Kg/m3.u Effect of fiber volume fraction and lengthu HP fibers = 6, 12, 24, 40 mmu HD fibers = 12 , 24 mmu Effect of Fiber in a Hybrid length u various lengths of fibers, at 10 Kg/m3u HP6-12 u HP6-24 u HP12-24 u HP6-12-24ClosedClosed--Loop Compression TestsLoop Compression Testsu A 450 KN closed-loop controlled testing machine. u two LVDTs measured the axial strain from a special ring type fixtureu Three replicate compression cylinders 76.2x152 mm long. Gage length 64 mm.u A chain type fixture with an extensometer was used to measure the transverse strain. u The axial mode controlled the prepeak-microcracking phase. u The circumferential displacement controlled post-peak response.Comparison of Axial and Comparison of Axial and Circumferential StressCircumferential Stress--StrainsStrains28 Days7 Days3 Days0 0.0005 0.001 0.0015 0.002 0.0025 0.003Axial Strain, mm/mm10203040Stress, MPa0.01 0.008 0.006 0.004 0.002 0Circumferential Strain, mm/mmW/C = 0.4HP12, Vf=10 Kg/m3Comparison of Axial and Comparison of Axial and Circumferential StressCircumferential Stress--StrainsStrains28 Days7 Days3 Days0 0.0005 0.001 0.0015 0.002 0.0025 0.003Axial Strain, mm/mmW/C = 0.4Vf = 10 Kg/m3051015202530Stress, MPa00.0020.0040.0060.0080.01Circumferential Strain, mm/mmHP12-24Effect of Curing Duration on Compression Effect of Curing Duration on Compression ResponseResponse--Effect of Volume FractionEffect of Volume Fraction28 Days7 Days3 Days0 0.002 0.004 0.006 0.008 0.01Circumferential Strain, mm/mm010203040Stress, MPaW/C = 0.4Vf = 10 Kg/m3HP1228 Days7 Days3 Days010203040Stress, MPa0 0.002 0.004 0.006 0.008 0.01Circumferential Strain, mm/mmW/C = 0.4Vf = 20 Kg/m3HP12Effect of Fiber Volume Fraction Effect of Fiber Volume Fraction on Compression Responseon Compression ResponseVf = 5 Kg/m3Vf = 10 Kg/m3Vf = 20 Kg/m3010203040Stress, MPa0 0.002 0.004 0.006 0.008 0.01Circumferential Strain, mm/mmW/C = 0.4Vf = 10 Kg/m3Vf = 5 Kg/m3Vf = 20 Kg/m3HP12_7W/C = 0.55HP1210_28HP1220_280 0.002 0.004 0.006 0.008 0.01Circumferential Strain, mm/mm010203040Stress, MPaW/C = 0.4Vf = 10 Kg/m3Vf = 20 Kg/m3Comparison of HP and HD fibersComparison of HP and HD fibers0.000 0.004 0.008 0.012Circumferential Strain, mm/mm010203040Stress, MPa28 days 7 days w/c = 0.55Vf = 5 Kg/m3 HP12mm ARGlass fibers0.000 0.004 0.008 0.012Circumferential Strain, mm/mm010203040Stress, MPa28 Days 7 Days w/c = 0.55Vf = 0.6 Kg/m3 HD12mmEffect of Fiber Length on Effect of Fiber Length on Compression ResponseCompression Responseu Mix type II0.000 0.002 0.004 0.006 0.008 0.010Circumferential Strain, mm/mm010203040Stress, MPaHP40 mmHP12 mmw/c = 0.55Vf = 5 Kg/m3ClosedClosed--Loop Flexure TestsLoop Flexure Testsu 89 KN closed-loop controlled testing machine. u one LVDT measured the deflection of the beam. u Three replicate flexural prisms 100x100x368 mm in dimensions. Notch length of 12 mm.u A crack mouth opening gage was used as the control parameter.Effect of Fiber Volume Fraction Effect of Fiber Volume Fraction on Flexural Responseon Flexural ResponseVf = 20 Kg/m3Vf = 10 Kg/m3Vf = 5 Kg/m3Control0 0.2 0.4 0.6 0.8 1Crack Mouth opening Displacement, mm024681012Load, KNAge = 28 DaysW/C = 0.4HP120 0.01 0.02 0.03 0.04CMOD, in05001000150020002500Load, lbs0 0.2 0.4 0.6 0.8 1CMOD, mm048Load, KNControl10 Kg/m320 Kg/m3Vf = 20 Kg/m3Age = 28 DaysHP 12mmW/C = 0.4Vf =10 Kg/m3ControlComparison of HP and HD fibersComparison of HP and HD fibers0.0